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Spectra VX

User’s Guide

response, so that a strong ground and weak quarter response

would look like:

The detector will see both signals at the same time, and the

combination of the two can be represented with a third vector as

follows:

The resulting signal appears to be a fairly strong ferrous tar-

get instead of a quarter. This is the downfall of the old TR-dis-

criminator designs. Fortunately, since the VDI response for

ground is usually far away from the response of desirable tar-

gets, there are ways to deal with it. In a modern VLF motion

discriminator, the receiver determines what part of the signal is

the ground response and, using special filter techniques, nor-

malizes the whole VDI scale to the current ground signal,

resulting in the ground signal being ignored. Graphically, this

looks like:

-95 +95

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White Spectra VX3 Bedienerhandbuch Seite 16